/**
 * Copyright (c) 2014 MongoDB Inc.
 *
 * This program is free software: you can redistribute it and/or  modify
 * it under the terms of the GNU Affero General Public License, version 3,
 * as published by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * As a special exception, the copyright holders give permission to link the
 * code of portions of this program with the OpenSSL library under certain
 * conditions as described in each individual source file and distribute
 * linked combinations including the program with the OpenSSL library. You
 * must comply with the GNU Affero General Public License in all respects for
 * all of the code used other than as permitted herein. If you modify file(s)
 * with this exception, you may extend this exception to your version of the
 * file(s), but you are not obligated to do so. If you do not wish to do so,
 * delete this exception statement from your version. If you delete this
 * exception statement from all source files in the program, then also delete
 * it in the license file.
 */

#pragma once

#include <boost/optional.hpp>
#include <set>
#include <string>

#include "mongo/db/pipeline/document.h"

namespace mongo {
    class ParsedDeps;

    /**
     * This struct allows components in an agg pipeline to report what they need from their input.
     */
    struct DepsTracker {
        DepsTracker()
            : needWholeDocument(false)
            , needTextScore(false)
        {}

        /**
         * Returns a projection object covering the dependencies tracked by this class.
         */
        BSONObj toProjection() const;

        boost::optional<ParsedDeps> toParsedDeps() const;

        std::set<std::string> fields; // names of needed fields in dotted notation
        bool needWholeDocument; // if true, ignore fields and assume the whole document is needed
        bool needTextScore;
    };

    /**
     * This class is designed to quickly extract the needed fields from a BSONObj into a Document.
     * It should only be created by a call to DepsTracker::ParsedDeps
     */
    class ParsedDeps {
    public:
        Document extractFields(const BSONObj& input) const;

    private:
        friend struct DepsTracker; // so it can call constructor
        explicit ParsedDeps(const Document& fields)
            : _fields(fields)
        {}

        Document _fields;
    };
}
